Earth Structure

Made up of igneous rocks - Granite and Grandodiorite - overlain by sedimentary, metamorphic and igneous rocks.

35km thick on average but can be up to 90km thick in places like mountain ranges.

It has a density of 2.7g/cm3 (cubed).

Oldest - can be up to 4 BILLION years old.

Is formed at the MOR.

Made of MAFIC igneous rocks - Basalt, Dolerite and Gabbro.

7km thick on average.

Density of 2.9g/cm3 (cubed).

Young - maximum of 200 million years old.

"Rocky Sphere" - rigid, solid and brittle upper mantle and crust.

Lithosphere is divided into tectonic plates (7 major and 6 minor).

The upper mantle has a density of 3.3g/cm3.

The boundary between the crust and the upper mantle (THE MOHO DISCONTINUITY) is at a depth of 35km.

"Weak Sphere" - RHEID = mostly solid but ductile and able to flow - 5% molten.
The asthenosphere is made of the lower mantle.

LOW VELOCITY ZONE = P and S waves slow down.

This sphere transfers heat via CONVECTION CURRENTS from the core to the surface.
Starts at temperatures of 1300 degrees Celsius.

It is the friction between the moving asthenosphere and the overlying rigid lithosphere that causes the tectonic plates to move.

The density of the lower mantle is 5.4g/cm3.

The boundary between the upper and lower mantle, the lithosphere and asthenosphere, is at a depth of 700km.

The entire mantle is made up of ULTRAMAFIC OLIVINE RICH ROCK known as PERIDOTITE.

(Mafic = rocks made of magnesium and iron).

Liquid nickel and iron.

Density of 9.9g/cm3.

The boundary between the mantle and the outer core is at a depth of 2900km and is known as the GUTENBERG DISCONTINUITY.

Solid iron and nickel.

Density of 13.5g/cm3.

Temperatures of 7000 degrees Celsius - it has heat producing elements such as Uranium, Thorium and Potassium and has residual heat left over from Earth's accretion.

The boundary between the outer core and inner core is at a depth of 5100km and is known as the LEHMANN DISCONTINUITY.